Continuity through the Power Prongs?

Hey, guys. I just bought a Cobra 29 LTD classic. I've tested the continuity for my 102" whip antenna and coax. Everything on the system that should have continuity has it, and everything that should be open is open from the coax up front to the antenna and base. I plug the coax into the back of the CB and everything still reads the same until I plug in the power.

As soon as I plug in the power, I have continuity between the base and the antenna all down the line. I checked the power feed from the 12 power to the back of the three prong plug for the unit and there's nothing. If I test the power prongs on the back of the CB, I get almost full continuity. I popped open the back of the unit to see if there was a short, and there's a small, flat, yellow capacitor soldered to the back of each prong leading to a ground spot on the back of the unit. That seems to be where the continuity is coming from.

If I unplug it, everything goes back to normal. Hots have continuity, grounds have continuity, but between the two, they're open. Is this normal? I'm a complete noob here, so any help would be greatly appreciated.

Thanks!
Chuck

 

Yes. It powers up and runs normally, but my SWR pegs off the charts no matter how I calibrate it.

 

Thanks for your help! All good points and I appreciate the detailed answer. The vehicle is a 1964 Plymouth Valiant that's just finished a frame off restoration. Entirely brand new Ron Francis wiring harness with a grounding kit run to all electrical components. Antenna mount is a steel bracket we fabbed up to go under the bumper for a side mount with a tie down over the driver's door. The bracket has a grounding wire run from it to a copper grounding bolt in the trunk that the rest of the rear electrical circuits tie into. That bolt has an 8 gauge wire running up to another copper ground bolt on the firewall at the front of the car connected to the main ground bus that everything else is connected to.

Thanks again for the advice!

 

Oh, and no, I wasn't trying to calibrate it with the antenna tied down. It was up. I was pulled off on a country road with cow pastures on either side of me. It's Florida so the ground is nice and flat.

 

Thanks! That sounds like a wild car. Not too many 273 B-bodies out there, and never heard of anything with those options.

I switched to a braided ground and man does that seem to make a world of difference. I added a fender washer to "lengthen" the antenna slightly and it did made the calibrations for 1 and 40 true. I was checking last night and the SWR was so low it barely moved the needle and got a response from someone over two miles away. Not bad! Thanks again for the advice. This will really help with my trip from Florida to Pennsylvania. We're leaving Wednesday and I'm driving the Valiant along with my friend's 1964 Dodge pickup and this will make communication between the two vehicles so much easier.